基于数字岩心的砂粒对储集层渗透特性影响

Impact of Sand Grains on Reservoir Permeability Based on Digital Cores

正确认识砂粒对储集层渗透特性影响,对砂砾岩油藏的合理开采具有重要的意义。基于岩心CT扫描图像,通过砂粒嵌入法构建砂砾岩数字岩心,运用最大球法提取相应的孔隙网络模型,利用逾渗理论研究砂粒对砂砾岩渗透率和残余油饱和度的影响。结果表明,砂粒的存在会降低岩心渗透率,增大残余油饱和度;随着砂粒位置向岩心出口端移动,岩心渗透率逐渐降低,残余油饱和度逐渐减小;砂粒的增大会阻断较多孔隙的连通性,使岩心渗透率降低,残余油饱和度升高;在此基础上建立了岩心渗透率、残余油饱和度与微观孔隙结构参数关系模型,模型预测结果与逾渗模拟结果一致性较好,岩心渗透率相对误差小于7.6%,残余油饱和度相对误差小于2.8%.

Accurate understanding of the effect of sand grains on reservoir permeability is significant for reasonable development of sandy conglomerate reservoirs. On the basis of CT scanning images of cores, digital cores of sandy conglomerate are constructed with sand-grain imbedding method, the corresponding pore network model is extracted with the maximum bail method and the impact of sand grains to permeability and residual oil saturation of sandy conglomerate is studied using percolation theory. The result shows that the existence of sand grains will decrease core permeability and increase residual oil saturation; with sand grains moving towards core outlet end, core permeability and residual oil saturation will gradually decrease; the increase of sand grain size will block flow paths among pores, which will result in the decline of core permeability and increase of residual oil saturation. Then a relation model between core permeability and micro-pore structural parameters has been established and the prediction result obtained from the model shows good consistency with the percolation modelling result, the relative errors of core permeability and residual oil saturation are less than 7.6% and 2.8%, respectively.